Valves are used in many applications wherein the control of the flow of a process fluid is needed. Such process fluids may include liquids such as oil, fuel, water, etc., or gases such as, e.g., natural gas, oxygen, etc. Some valves operate to meter the flow of fluid therethrough and operate by accurately positioning the valving member to control the amount of fluid allowed to pass through the valve. Other valves operate in a switching fashion wherein the flow of fluid therethrough is either turned on or turned off. Such valves may be utilized, for example, in consumer and commercial appliances such as washing machines, etc., whereby water is allowed to flow for a predetermined period of time or until a predetermined volume has been dispensed therethrough. The control of the operation of such valves is typically performed by an electronic control circuit, such as a micro processor-based controller, along with its associated drive circuitry, to open and/or close the valving member within the valve.
A problem with such switching valves is the force necessary to open the valving member against the static pressure of the process fluid acting on one side of the valving member. Depending on the application, this pressure may be quite high, particularly when compared with the low pressure on the opposite side of the valving member which, in many appliance applications, is at atmospheric pressure. In addition to the static fluid pressure acting on the valving member tending to keep it closed, many such switching valves also include a spring positioned to apply a force on the valving member. This spring force allows the valve to be closed upon the removal of a drive signal, and maintains a bias force on the valving member to keep it closed.
In such configurations, the valve actuator must overcome both the static fluid pressure, which can be quite high and may vary from installation to installation, as well as the spring force, both of which are acting to keep the valve closed. Once these two forces have been overcome, however, the force necessary to continue to open the valve to its fully open position is substantially reduced as the pressure differential across the valving member face drops dramatically. Once this pressure has been equalized, the only remaining force against which the actuator must act is the spring force.
Many electronically controlled switching valves include an electrically actuated solenoid to directly act on a plunger connected to the valving member to move the valving member to its open position. Unfortunately, due to the high pressure differentials that exist for a closed valve and the spring force, the actuator needs to be relatively large so that it is able to reliably operate the valve under all operating conditions and installations. In many industries, such as the consumer appliance industry, strict Governmental and certifying agency requirements place a heavy premium on an electric power usage. As such, these direct acting solenoid controlled valves that include solenoids sized to reliably open the valving member provide a significant disadvantage to the appliance manufacturer in being able to attain agency certification as, for example, as an Energy Star appliance rated appliance. Further, the appliance industry is highly competitive and the cost of such large solenoid actuators also provides a significant detriment to their use.
To overcome these problems many manufacturers have gone to a pilot valve design that allows for a significantly reduced size solenoid actuator to be used to operate the valve. Specifically, a pilot operated valve utilizes a relatively small solenoid to be used to move a plunger to open a small pilot valve having a small pilot opening in the valving section. When opened, this pilot valve allows a small amount of water to flow and open a diaphragm using the principle of differential pressure and surface area. The diaphragm then opens the main valving member that controls the main flow of the process fluid. In other words, pilot operated valves take advantage of the energy of the process fluid pressure to do most of the work to open and close the valve.
Since the solenoid now need only open the small pilot valve, its size may be substantially reduced. This small size results in a lower energy usage as well as lower costs, both providing a significant advantage in many industries, such as the consumer appliance industry. As a result, appliance manufacturers, such as the assignee of the instant application, provide literally millions of pilot operated water valves each year.
Typical small solenoids include a solenoid coil of approximately 7055 turns of 38 AWG (American wire gauge) gauge copper wire wound on a bobbin, which uses approximately 28 grams of copper. The coil and bobbin are then over molded within encapsulation. The solenoid also includes a ferromagnetic pole frame having an air gap in the magnetic path thereof. The ferromagnetic pole frame is constructed from a pair of brackets.
While the typical pilot operated water valves provide a substantial reduction in the solenoid actuator size, and therefore cost, over direct acting solenoid actuated valves, the solenoids still rely on copper wire windings to generate the magnetic force needed to operate the pilot valve actuator. Unfortunately, the cost of copper has increased more than three hundred percent in recent years. This significant price increase has significantly increased the cost of the solenoid actuator coil to a point where the solenoid coil now provides a significant cost of the valve as a whole (about fifty percent). Unfortunately, in such a competitive industry, the difference of only a few cents can make or break a major sale. With the forecast showing continuing increases in the cost of copper as well as other raw materials used to construct the solenoid actuators, there existed a need in the art for a new solenoid coil design that reduces the material costs by reducing the amount of copper used to form the solenoid coil. Countering this copper reduction effort, however, is the requirement for reliable operation at each actuation and continued long life of such valves.
These conflicting requirement lead to the development of a new solenoid design for a pilot operated water valve having reduced material costs that still provides reliable actuation and long operational life. Such a solenoid is described in co-pending application Ser. No. 12/178,977, entitled Solenoid For A Pilot Operated Water Valve Having Reduced Copper And Increased Thermal Efficiency, filed on Jun. 24, 2008, and assigned to the assignee of the instant application, the teachings and disclosure of which are incorporated in their entireties herein by reference thereto. Such a solenoid includes a magnetic pole frame that is positioned around the coil of 40 AWG copper wire with a height to width ratio of substantially less than one.
While such a solenoid provides significant advantages over prior solenoid operated pilot valves, the short-fat configuration of the coil assembly introduces difficulties in securing the coil assembly to the water valve itself. Prior castle-top configurations integrated into the solenoid guide tube have proven not to be viable due to height restrictions in the overall design. As such, an attachment mechanism that can secure the coil assembly of a solenoid to the pilot operated water valve is needed.
Embodiments of the invention provide such a coil capture apparatus and method of mounting a coil to a water valve. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.